Move more internal methods from GrContext to GrContextPriv (take 2)

Change-Id: I47108910517d61edeb52f82793d384fdb5605d45
Reviewed-on: https://skia-review.googlesource.com/97241
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
35 files changed